Sunday, January 07, 2007

Have Humans Stopped Evolving?

Yesterday's Quirks & Quarks radio show had a segment on human evolution. Here's the description from their website:

January 6, 2007: Are Humans Still Evolving?

Evolution has made us what we are today, and we're increasingly learning what made modern humans different from our ancestors. But many scientists think that we have now removed nature's control over our genetic legacy. Our technology allows us to control our environment and survival to the degree that we may have stopped human evolution altogether. Is our growth and development as a species at a standstill? If not, what will we become in the future? Find out this week on Quirks & Quarks.

Listen to the podcast. The segment on human evolution starts about one third of the way through the show.

The idea that humans have stopped evolving is ridiculous. It reflects a deep and fundamental misunderstanding of evolutionary theory.

Fortunately, the blurb on the website doesn't reflect what was broadcast. The host, Bob McDonald actually does a very good job of sorting through the rhetoric and the show is an excellent summary of current scientific thinking. It's by far the best thing about the rate of human evolution that I've ever heard on public radio.

One of the people interviewed on the show is Steve Jones from University College, London. Jones claims that almost everyone is reproducing these days so natural selection isn't affecting humans any more. He contrasts the situation today with that in Shakespeare's time when 2 out of 3 babies didn't survive to adulthood.

This is one of the weaker parts of the show. The claim that natural selection isn't working on humans is false. It is refuted by Jones himself later on in the broadcast, and by Noell Boaz from Ross University in Dominica.

Let's deal with the increase in longevity that we've seen in some societies over the past 500 years. We'll dismiss the obvious bias in equating what happens in Caucasian societies with evolution of the entire species. What about the fact that people in London live longer today that they did in 1600? Does this have anything to do with evolution?

Jones thinks so. He says,

Now a lot of those deaths in the old days were due to genetic differences but if everybody stays alive, everybody gets through, no more natural selection.

I don't think so. It isn't obvious to me that people were surviving in 1600 because they had better genes. People died for all kinds of reasons that had nothing to do with genes. A famous example from the nineteenth century was the London cholera outbreak. In that case, you died if you were close to the contaminated Broad Street Pump and not because you had bad genes.

If you died of infection or malnutrition in 1600 it was probably due to bad luck and not bad genes. As living conditions improved, everyone benefited equally, not just those who might have been genetically susceptible. Thus, natural selection wasn't all that important back then and most of the improvements in health in developed countries have affected evolution directly. (The quibblers are waiting to pounce, so let me address two objections to that statement. First, there are other, more modern, medical advances that do affect selection—wait for them. Second, there are some examples of genetic effects on whether you survive disease. Some people might have been more resistant to the Black Plague, for example. Such examples are exceptions to the rule. The common assumption that most deaths in the past had something to do with natural selection is what I'm addressing here.)

So, let's be skeptical about the specific argument that Jones is making, namely that increased longevity, per se, is proof that the effect of natural selection is diminished in modern societies. A lot of negative selection—selection against less fit individuals—is still taking place in utero just as it always has. Lethal mutations result in spontaneous abortion or failure to produce viable sperm and eggs. This form of natural selection hasn't changed significantly. Also, even though severely handicapped children born today may survive longer, they probably won't reproduce.

On the other hand, there are medical advances that do affect natural selection. The most obvious one is the invention of eyeglasses. As Jones points out in the show, people with a genetic disposition for bad eyesight can now survive whereas back in the hunter-gatherer days it might have been much more difficult. Thus, natural selection in favor of good eyesight has been relaxed because of eyeglasses.

What does that mean for human evolution? To its credit, the Quirks & Quarks show doesn't jump to the false conclusion so common among the general public. Evolution hasn't stopped, it has increased! The removal of negative selection causes previously detrimental alleles to survive in the population; therefore, their frequency increases. Thus, evolution is happening today but was blocked by negative selection in the past.

The same argument applies to all medical advances that allow for previously handicapped individuals to survive in modern society. Human evolution is being accelerated. This is a point worth emphasizing because the opposite conclusion is so common. Most people think that removing strong negative selection means that evolution has stopped when, in fact, the exact opposite is true! The misconception arises because the general public thinks of evolution as a progressive improvement in the gene pool. Modern medicine is allowing "defective" individuals to survive. This can't be evolution according to that false understanding of evolution. (There are other things wrong with that false argument; namely, the concept that people with myopia or diabetes are somehow lesser citizens. This isn't the place to get into that discussion.)

Strong negative selection acts as a brake on evolution. It slows evolution down. Remove the brake, and evolution speeds up.

There's more to evolution than natural selection. Bob McDonald interviews Katherine Pollard from the University of California, Davis. She points out that much of evolution is due to random genetic drift. Drift has nothing to do with natural selection, so whether or not selection has decreased will play only a minor role in whether humans are evolving. You can't stop drift and you can't stop mutations. You can't stop human evolution. As McDonald puts it, "we still will evolve ... it's not the kind of evolution we imagine."

Evolution is not just the result of survival of the fittest. Furthermore, it is not progressive in spite of the fact that this misconception is widespread. As McDonald says in closing, "... this is an illusion about the way that evolution works. Evolution has never guaranteed improvement or progress, just change."

Change is good. It's good that humans are evolving. Things can only get better, right?

26 comments:

On the other hand, there are medical advances that do affect natural selection. The most obvious one is the invention of eyeglasses. As Jones points out in the show, people with a genetic disposition for bad eyesight can now survive whereas back in the hunter-gatherer days it might have been much more difficult. Thus, natural selection in favor of good eyesight has been relaxed because of eyeglasses.

Not quite; we may be able to deal with foggy vision a bit better than before, although I'm not quite sure about that.

But we do need much better eye-muscle coordination than before. It's not about throwing a spear at a moving target every day or so; it's about maneuvering a one-ton bullet through 6 lanes of traffic for hours, while seriously sleep-deprived. And that affects survival as directly as hunting did.

This aspect of evolution can and has been tested by taking humans in one of their most sexually active stages and artificially crowding them into an enclosed structure. I think it's called a "High School".

In this exaggerated environment, even the slightest misstep can result in the loss of a potential mate, a poorly chosen word, provoking a bullying response from a competitor, even a minor facial blemish. In this hyper-charged environment, social graces and conformity to cultural norms can often ensure successful mating.

Of course, some members of the species look to other than the superficial aspects of a potential mate and look for more intangible qualities, such as loyalty, sensitivity, intelligence. But this is also evolution, of course.

There hasn't been a new genus in 2 million years and a new true species in historical times. All that can be documented is extinction without a single replacement or any new species to occupy any novel new niches. Intraspecific varieties and subspecies are all that the Darwinian model has ever been able to generate. None of these are incipient species. Creative evolution is finished and has been for a very long time. All we see today is rampant extinction. Pierre Grasse realized it as did Otto Schindewolf, Robert Broom and John A. Davison.

Sorry about that.

Now please don't delete this comment as so many blogczars, like Spravid Dinger and Esley Welsberry are prone to do. I don't want to have to start calling you Marry Loran don't you know.

But we do need much better eye-muscle coordination than before. It's not about throwing a spear at a moving target every day or so; it's about maneuvering a one-ton bullet through 6 lanes of traffic for hours, while seriously sleep-deprived. And that affects survival as directly as hunting did.

I'm not sure if I agree that it is a matter of eye coordination. Maybe, maybe not. But I do like the idea of thinking of selection in relation to driving.

As a matter of fact Homo sapiens is apparently the youngest mammal species to appear on earth and in my view the last mammal to ever appear. We are no more than 100,000 years old. I am also confident that Naanderthal was our immediate ancestor simply because there was no other candidate available when we first appeared. It is also possible that Homo sapiens was produced on more than one occasion. Apparently we represent the terminus of a "prescribed" evolution. All that remains is extinction which is all that can presently be verified.

As a matter of fact Homo sapiens is apparently the youngest mammal species to appear on earth and in my view the last mammal to ever appear

John:

The earliest modern human fossils predate the earliest Neanderthal fossils by a few thousand years and are found many thousands of miles away. If we extend the record for both groups in a reasonable way using the stone tool record (which leaves more evidence) then this reamins true but the modern humans or their immediate ancestors are hundreds of thousands of years earlier than the earliest neanderthals.

And humans came on the scene only once.

If dogs are a different species than wolves, they are an example of a more recently evolved species.

Your assertion that humans are the most (let's say "one of the most" recent species is probably not very far from the truth, though, because during the latter part of the Pleistocene, most of the action in Mammal World has been extinction not speciation but it is during this time that humans arose.

Regarding Prescribed Evolution ... I think it is only fair that Professor Moran field that one ... this is his blog site after all....

All dogs are wolves or if you prefer all wolves are dogs. The hybrids beteen dogs, coyotes and wolves are all fertile.

As for humans, I am defining humans as modern man (Homo sapiens.) You are definitely wrong of you think that Homo sapiens is older thamn Neanderthal. I repeat that Homo sapiens is the youngest mammal ever to appear on earth and he has not evolved a micron since his initial appearance. If anything he has accumulated a number of deleterious genes that will, if it continues, lead to his early extinction, if he doesn't commit suicide first by destroying his environment. That, he seems bound and determined to achieve.

Just because wolves and dogs can make fertile wolfdogs doesn't mean they are the same species. You wrongly believe that total reproductive isolation is required for two species to be, well, species. You may have a point that the definition of species isn't very clear cut and hotly debated in biology, but wolves and dogs are different species. By way of analogy (and ripping off of Dawkins) human beings are the product of an unbroken line of ancestors all the way back to, arbitrarily, an ancestral eukaryote cell. That is, I could mate and yield fertile offspring with my immediate ancestor (were they still living); that ancestor could do the same with its immediate ancestor, etc. until our eukaryote cell. Yet, at the end of the day, I am not of the same species as the ancestral eukaryote cell. Another example would be ring species

Wikipedia is nothing but a willing dupe for Darwinian mysticism. Darwinism in all its disguises never had anything whatsoever to do with creative evolution, absolutely nothing. Got that? Write that down.

you make your argument based on a technicality. I know the definition of evolution for scientists means change can happen in both directions. This is where I think the genaral public's misconception should be given more credence because it not a bad thing for them to think evolution is progressive. The word is EVOLUTION , not REVOLUTION, so the 'official' meaning of the term should IMO be changed to reflect this.Or at least have an addendum term everyone can remember that means precisely forward evolution. Afterall, what amount evolution would take place if progress didn't happen sequentially? None. We'd still be bacteria if we took two steps back for every one forward. Thats not to say these organisms are any less important, they provide the base we stand on. People with disabilities are not lesser beings, but they do have lessfit bodies, and despite what you say, thats still important. Genetic drift is important mainly for small populations, but there are 7 billion of us , more biomass than any other land animal outside of insects.We're now constantly mingling and fixation of alleles is becoming less likely( at least in the short term).People base some of their assumption thaty evolution has stopped based on what is going to happen in the near future, where deleterious/recessive alleles are no longer selected against. but reach a kind of nominal distribution. Blond people are not going to become extinct just a lot less of them. As you stated natural selection is becoming less important as people have changed the environment making it much easier for people with minor disabilities to get along. Culture has evolved to a level were we think that the mental is at least as important as the physical. If they have them, people with mental conditons can often be treated more effectively than physical conditions. Or they can hide these traits to pass on thier genes. Another biggy I'll just open on is that of unnatural selection.We're coming up to a time when genes can be screened or altered and so everyone's genetic profile can be made almost uniform.Evolution will have really stopped then. People have awareness about this.I remember a 60's Twilight Zone ep that dealt with this very concept. More importantly WWII was all about that. The Scientists have too big an ego and dont want to change for even something thats logical when that is supossed to be the mantra.

I would argue that natural selection has stopped in modern humans because anyone can reproduce. The vast majority of people can and do reproduce and fitness has absolutely zero to do with it. In fact qualities that many would consider to represent "fitness" like intelligence or the ability to gather resources and status have nothing to do with reproductive fitness. As an example, your local biology professor who makes an income far above average may have 2 or 3 kids, while a welfare mom in the slums might have 7. But the point is, no matter how tall you are, how fat you are, how poor or rich you are, there is a human somewhere, sometime who will reproduce with you. So there doesn't seem to be much selection going on.

Sorry, but being able to manipulate the environment drastically changes the rate at which we evolve. It's mathematics....the more drastic or the more variance in the environment, the faster you evolve. We've brought evolution down o a screeching halt...this is simple mathematics, if you believe in evolution, then you cannot dispute this without sounding superstitious.

I agree that we may be evolving, but I do not agree that it's in an upward direction. My reasoning behind this is that we have almost overcome all natural predators. We have evolved enough to learn and create ideas, and that knowledge will always grow, allowing us to do things like create better medicine that allows us to live longer than previous generations. This is not the human race evolving; it's only medicine that prolongs our lives. At this point, the only way to evolve upward would be selective breeding or the emergence of a new predator on Earth.

My feeling is, and I state it as such, not as assertion of fact, that no matter what control we think we exert over such things as environment or evolution we remain at the mercy of the universe. All our concepts of human superception are selfindulgent fantasy.Sure, we can do more than our distant ancestors, but less as well. For every advance, something is left behind. The mistake is in assuming early man to be a helpless victim of his environment. Feared as a savage and furious predator, even the mighty mammoth fell to these relentless packs of vicious pointed stick wielding beasts.My point is that we are and likely will always remain part of, and as such subject to, nature. All our illusions are just that. Illusion. We're not alone in using tools to master tasks, nor does our expertise absolve us from nature. Quite simply, the higher you climb the further you can fall.Planet of the Apes anyone? :)

As of right now I think that evolution has slowed to a significant crawl. At this rate I mean that people will still look like people even 50 million years from now (Not counting everyone becoming brown skinned, men becoming more effeminate or women being the same size as men, or everyone getting bigger. All these will continually progress or regress depending on cultural evolution as the primary force). Even genetic drift doesn't really matter. It works neatly in a lab (I did the probability experiment for my minor in genetics) but it doesn't work nearly as well in actuality. It's not nearly as strong a force evolutionists make it out to be. This is because of genetic fail safes that are responsible for much of the very spontaneous abortions you mention. Some combinations of genes just don't work. That's how one prediction put forward by drift theory, death spirals in a small enough population, occurs. Another thing is that we now have a permanent social memory, so we'll be immediately cognizant of any major changes and put a stop to them.

But human evolution will happen nonetheless , quite soon. But it will be due a new force; artificial selection

Another point is that I wish evolutionists would make up their mind about what evolution is. I learned in uni that evolution is the tendency towards greater complexity, speciation and nichification. But then I also learned it encompasses any change, at all, in gene representation. These two definitions are NOT mutually inclusive. Maintenance of a present state or regression from a present state that doesn't lead to forward evolution (new species) and may in fact likely lead to or cause extinction should be termed steady state equilibrium and devolution.

Sorry for the late reply - I have just come across this article, and it is a subject that I find very interesting. My own view is that humans have certainly changed the prospects for differential reproductive success for both themselves and many other species on the planet. In the past, there were always many random, non-genetically determined deaths. However there was also an underlying level of success that was dependent in some way on an individual's genes, whether those genes provided a more robust body or some mode of behavior that was better suited to the environment (both the external environment and also the other members of the species that one had to interact with to succeed sexually and often for cooperative survival).

Today, this is still true for most non-human species. We breed our farm and domestic animals to please us, and those with genetic profiles that do not do so are slowly bred out of the gene pool. Bad luck. Even for other species, our effect is undeniable, and often not related to the success factors of the past - flies entering a house with a fly swatter are a lot less likely to reproduce, and perhaps one day they will evolve a gene to sense the presence of the fly swatter before entering. Crazy? Maybe an extreme example, but are you sure there is no distinctive odor given off by fly swatter plastic?

For humans however, the situation is now a lot less clear. Certainly in western societies, there is little incentive to do anything to enhance your survival prospects in order to reach reproductive age. Other than accidental death, there is very little that can stop a human from breeding. No need for intelligence, diligence, foresight, and the like. The state will provide. The only real requirement is some facility in attracting the opposite sex. For females, this is usually not a problem - sex is there for the taking, and if the father doesn't stick around to provide for the offspring, the state will step in and take care of it. And for males, there is always either violence, or social lying ("Of course I'll still love you in the morning".) In fact the strong favorites for reproductive success are those people, male and female, that disavow any need to plan for the future or even the present, and simply concentrate on reproduction. The state will provide for both us and our children, at least to a very minimal standard. But what more do you really need? And sex and cheap alcohol and drugs are a convenient and largely unregulated source of comfort, and the kids' welfare payments are a very useful source of income. As long as you have enough kids, of course.

Those of you who have seen "Idiocracy" (a very bad movie, but with a very valid point) will understand what I mean. The dumb jock has already sired 10 children in high school and has two dozen grandchildren by the age of 35, while the conscientious middle class "brainiacs" of the graduating class are still wondering if 35 is too soon to have their first child.

The same situation is playing out around the world, with non-replacement birth rates in many western countries, while the third world birth rate (and importantly their survival rate) continues to grow. Of course, there are many reasons for this: the cultural need to have many children to support one's old age, overt and covert violence by males towards females, simple unavailability of the means for birth control. But the end result is the same. The species evolves.

I realize this sounds very racist, classist, and probably several other kinds of non-politically correct -ism's. And of course, the past was not always great either, with a premium often available to those males inclined towards violence, whether personally as in rape, or through the aggrandizement of power and riches to the warrior class. But we are certainly "evolving" in the sense that we are changing the genetics of what is required for reproductive success, and in fact are loosening the parameters of success significantly.

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Principles of Biochemistry 5th edition

Disclaimer

Some readers of this blog may be under the impression that my personal opinions represent the official position of Canada, the Province of Ontario, the City of Toronto, the University of Toronto, the Faculty of Medicine, or the Department of Biochemistry. All of these institutions, plus every single one of my colleagues, students, friends, and relatives, want you to know that I do not speak for them. You should also know that they don't speak for me.

Superstition

Quotations

The old argument of design in nature, as given by Paley, which formerlyseemed to me to be so conclusive, fails, now that the law of natural selection has been discovered. We can no longer argue that, for instance, the beautiful hinge of a bivalve shell must have been made by an intelligent being, like the hinge of a door by man. There seems to be no more design in the variability of organic beings and in the action of natural selection, than in the course which the wind blows.

Charles Darwin (c1880)Although I am fully convinced of the truth of the views given in this volume, I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of facts all viewed, during a long course of years, from a point of view directly opposite to mine. It is so easy to hide our ignorance under such expressions as "plan of creation," "unity of design," etc., and to think that we give an explanation when we only restate a fact. Any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject the theory.

Charles Darwin (1859)Science reveals where religion conceals. Where religion purports to explain, it actually resorts to tautology. To assert that "God did it" is no more than an admission of ignorance dressed deceitfully as an explanation...

Quotations

I have championed contingency, and will continue to do so, because its large realm and legitimate claims have been so poorly attended by evolutionary scientists who cannot discern the beat of this different drummer while their brains and ears remain tuned to only the sounds of general theory.

The essence of Darwinism lies in its claim that natural selection creates the fit. Variation is ubiquitous and random in direction. It supplies raw material only. Natural selection directs the course of evolutionary change.

Rudyard Kipling asked how the leopard got its spots, the rhino its wrinkled skin. He called his answers "just-so stories." When evolutionists try to explain form and behavior, they also tell just-so stories—and the agent is natural selection. Virtuosity in invention replaces testability as the criterion for acceptance.

The first commandment for all versions of NOMA might be summarized by stating: "Thou shalt not mix the magisteria by claiming that God directly ordains important events in the history of nature by special interference knowable only through revelation and not accessible to science." In common parlance, we refer to such special interference as "miracle"—operationally defined as a unique and temporary suspension of natural law to reorder the facts of nature by divine fiat.

Quotations

My own view is that conclusions about the evolution of human behavior should be based on research at least as rigorous as that used in studying nonhuman animals. And if you read the animal behavior journals, you'll see that this requirement sets the bar pretty high, so that many assertions about evolutionary psychology sink without a trace.

Jerry Coyne
Why Evolution Is TrueI once made the remark that two things disappeared in 1990: one was communism, the other was biochemistry and that only one of them should be allowed to come back.

Sydney Brenner
TIBS Dec. 2000
It is naïve to think that if a species' environment changes the species must adapt or else become extinct.... Just as a changed environment need not set in motion selection for new adaptations, new adaptations may evolve in an unchanging environment if new mutations arise that are superior to any pre-existing variations

Douglas Futuyma
One of the most frightening things in the Western world, and in this country in particular, is the number of people who believe in things that are scientifically false. If someone tells me that the earth is less than 10,000 years old, in my opinion he should see a psychiatrist.

Francis Crick
There will be no difficulty in computers being adapted to biology. There will be luddites. But they will be buried.

Sydney Brenner
An atheist before Darwin could have said, following Hume: 'I have no explanation for complex biological design. All I know is that God isn't a good explanation, so we must wait and hope that somebody comes up with a better one.' I can't help feeling that such a position, though logically sound, would have left one feeling pretty unsatisfied, and that although atheism might have been logically tenable before Darwin, Darwin made it possible to be an intellectually fulfilled atheist

Richard Dawkins
Another curious aspect of the theory of evolution is that everybody thinks he understand it. I mean philosophers, social scientists, and so on. While in fact very few people understand it, actually as it stands, even as it stood when Darwin expressed it, and even less as we now may be able to understand it in biology.

Jacques Monod
The false view of evolution as a process of global optimizing has been applied literally by engineers who, taken in by a mistaken metaphor, have attempted to find globally optimal solutions to design problems by writing programs that model evolution by natural selection.